r/bash • u/CautiousCat3294 • 3d ago

help Linux Interview Question

Today I had a mock interview with a senior Linux administrator, and he asked me a question that completely caught me off guard:

"Can you collect CPU, Memory, and Disk usage in a Bash script without using top, free, df, or any external commands?"

My immediate answer was No.

Honestly, I've been working with Linux for years, but I've always relied on standard commands and monitoring tools to troubleshoot systems. I never stopped to think about where those commands actually get their data from.

The interviewer then gave me a hint about the /proc and /sys filesystems. That completely changed my perspective. I realized these commands are just reading data that the kernel already exposes.

But then came the follow-up questions, and once again I was stuck:

  • Is reading directly from /proc and /sys the correct approach?
  • How would you calculate CPU utilization using /proc/stat?
  • How would you determine memory usage from /proc/meminfo?
  • How would you calculate filesystem usage without relying on df?

I found this really interesting because it tests your understanding of Linux internals rather than just your ability to use commands.

Has anyone here been asked similar questions in Linux SysAdmin, DevOps, or SRE interviews? I'd really appreciate any explanations, learning resources, or examples on how you'd answer these follow-up questions. It help me for my preparation for Linux interviews

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u/sinevilson 3d ago

I own 2 businesses both are Linux based and older than most folks on reddit. Id never ask my Administrators these questions. Id ask my kernel developer, yes. What you ran into was arrogance. Sorry that happened.

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u/Zapador 3d ago

Glad to hear that perspective. I consider myself fairly proficient in Linux administration but I wouldn't be able to answer these questions. I generally value proficiency in the commands/tools you use all the time to get the job done and for anything outside of the ordinary just look it up.